1. Field of the Invention
The present invention relates to an axial fan and a fan assembly.
2. Description of the Related Art
A recent innovation in motor technology has improved efficiency of axial fans (or a reduction in power consumption of the axial fans). Moreover, to further improve the efficiency of the axial fans, various techniques have been contrived concerning the shape of blades. JP-A 2000-110772, for example, describes a fan in which a motor is supported on an outlet side. In the fan described in JP-A 2000-110772, a housing, which is located radially outside of an impeller to surround the impeller, and a motor support portion, which is configured to support the motor, are joined to each other by support ribs arranged on the outlet side of the impeller.
When each of the support ribs arranged on the outlet side of the impeller is structured in the shape of a blade called a stationary vane, an air flow caused by rotation of the impeller can be controlled by the support ribs. This contributes to reducing the likelihood that an eddy will occur in the air flow sent from the impeller. The impeller is configured to generate the air flow through the rotation thereof, and if the air flow is a laminar flow, only a small windage loss will occur, whereas if the air flow is a turbulent flow (i.e., if an eddy occurs), a large windage loss will occur. Therefore, when the support ribs are arranged to function as stationary vanes to reduce the likelihood that an eddy will occur, an increase in efficiency of the fan is achieved.
However, in the case of an axial fan in which support ribs (or stationary vanes) are arranged on an inlet side of an impeller, a contrivance in the shape of the support ribs could not be expected to produce a flow control effect on an air flow on an outlet side of the impeller. Therefore, in the case of the axial fan in which the support ribs are arranged on the inlet side of the impeller, a method other than the above method of allowing the support ribs to function as the stationary vanes is required to achieve a reduction in the windage loss.